docs: session management docs

[paanSinghCoder]

Summary

Added comprehensive documentation for Frontier's session management, covering SDK integration, session lifecycle, metadata tracking, and gRPC APIs.

Changes

• Added new docs/authn/session.md documentation page
• Added "Session Management" to sidebar navigation
• Removed broken links from introduction.md and api-auth.md

Technical Details

Key topics covered:

• Session lifecycle (creation, validation, tracking, expiration)
• Session metadata (browser, OS, IP, location) and tracking fields (last active, isCurrent)
• SDK's built-in UI for viewing and revoking sessions
• Automatic activity tracking via useLastActiveTracker (10-minute interval, stored in FrontierContext)
• 5 gRPC APIs: 3 user APIs (ListSessions, RevokeSession, PingUserSession) and 2 admin APIs (ListUserSessions, RevokeUserSession)
• Integration best practices with code examples

Important notes:

• Session APIs are internal to SDK, not for direct client use
• Activity tracking does NOT extend session validity, only updates UI timestamp
• All session UI is built into SDK, no custom implementation needed

Test Plan
[x] Manual testing completed
[x] Build passes (npm run build successful)
[x] No broken links or build errors

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Project	Deployment	Preview	Comments	Updated (UTC)
frontier	Ready	Preview	Comment	Nov 13, 2025 11:45am

[coveralls]

Pull Request Test Coverage Report for Build 19330414254

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 37.614%

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Totals
Change from base Build 19328916859:	0.0%
Covered Lines:	15634
Relevant Lines:	41564

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💛 - Coveralls